Self-proportioning fluid dispensing apparatus

ABSTRACT

This disclosure relates to gasoline dispensing including an intermediate grade pump interconnected to both the premium grade storage tank and the regular grade storage tank through a blending valve. The blending valve includes a pair of flow passageways. A common throttling valve inversely varies the flow through the two passageways. A manual control valve is provided to adjustably and inversely set the cross-sectional areas of the flow passageways. The throttle valve is connected to a hydraulic diaphragm actuator having pressure chambers to the opposite sides of a movable diaphragm. Signal pressure lines connect the passageways between the two valves to corresponding pressure chambers to position the diaphragm and throttling valve to establish equal pressures in the passageways.

llnited States Patent [72] Inventor Charles D. Erickson Erie, Pa. [21] Appl. No. 762,890 [22] Filed Sept. 26, 1968 [45] Patented Feb. 23, 1971 [73] Assignee A. O. Smith Corporation Milwaukee, Wis.

[5 4] SELF-PROPORTIONING FLUID DISPENSING APPARATUS 7 Claims, 3 Drawing Figs. [52] [1.8. Cl 222/57, 222/134; 137/100 [51] Int. Cl B67d 5/56, 605d 1 l/02 [50] Field ofSearclh 222/134, 57; 137/100 [5 6] References Cited UNITED STATES PATENTS 1,985,918 1/1935 DeLancey 222/134X 2,145,] 14 1/1939 Gibbs et a1 137/100X 2,883,996 4/1959 Blewett et a1. 222/134X 3,195,669 7/1965 Court 137/100X FOREIGN PATENTS 690,247 7/1964 Canada 222/134 Primary Examiner-Robert B. Reeves Assistant Examiner-Frederick R. Handren Attorney-Andrus, Sceales, Starke & Sawall ABSTRACT: This disclosure relates to gasoline dispensing including an intermediate grade pump interconnected to both the premium grade storage tank and the regular grade storage tank through a blending valve. The blending valve includes a pair of flow passageways. A common throttling valve inversely varies the flow through the two passageways. A manual control valve is provided to adjustably and inversely set the crosssectional areas of the flow passageways. The throttle valve is connected to a hydraulic diaphragm actuator having pressure chambers to the opposite sides of a movable diaphragm. Signal pressure lines connect the passageways between the two valves to corresponding pressure chambers to position the diaphragm and throttling valve to establish equal pressures in the passageways.

SELF-PROPDRTIONING FLUID DISPENSING APPARATUS This invention relates to a dispensing system employing a blending valve means to establish a mixture of at least two materials and particularly to a gasoline dispensing system having means to dispense a selected blend of two standard grades ofgasolines.

Gasoline has been generally marketed under either of two grades or octane ratings respectively identified as regular gasoline and premium" gasoline. The recent development of automobiles has made it desirable to provide another octane rating intermediate the conventional regular and premium grade. Dispensing devices have been suggested which are interconnected to the storage tanks for both the regular and the premium gasolines. A manual adjustable control is provided to permit the selection of either regular or premium gasolines or some combination of such products. Such devices require relatively complicated mechanisms aseach grade or blend which is dispensed must also be interconnected into the com puter mechanism to provide a proper visual volume registration and visual cost registration in accordance with the volume dispensed. lndividual meters for each gasoline are normally provided within each pump and interconnected through a suitable integrating means to provide a suitable register output in accordance with the quantities of the two basic gasolines dispensed. Such systems are relatively expensive to construct and to maintain.

The present invention is directed to a simplified and relatively inexpensive dispensing system wherein completely separate dispensing units which may be of identical single product dispensing construction are provided for dispensing each of the several grades of gasoline. Thus, the system for a service station may include a regular" dispensing pump, a premium" dispensing pump and an intermediate of blend" dispensing pump of the same construction. The intermediate grade pump is interconnected to both the premium grade storage tank and the regular grade storage tank through a separate adjustable blending valve which is manually adjustable to establish a desired blend. Theregister of the intermediate grade pump is then set at a fixed price in accordance with the usual price adjustment of a pump.

In a particularly novel aspect of the present invention, the blending valve includes a pair of flow passageways from the individual liquids to a' common or blend outlet. A common throttling valve means inversely varies the flow through the two passageways. A manual control valve means is provided to adjustably and inversely set cross-sectional areas of the flow passageways. The relative positions of the two valve means establishes a control pressure condition in the two flow passageways which is coupled through a suitable actuator to automatically set and hold the throttling valve in a desired position.

As applied to a service station pump, the blending valve is provided with a pair of inputs connected respectively to the premium grade storage tank and the regular grade storage tank and a common output interconnected to the two passages through a suitable check valve construction. The throttle valve means or structure is adapted to inversely vary the flow passageway from the two inlets to the single outlet. The throttle valve means is connected to a hydraulic actuator such as a diaphragm actuator having pressure chambers to the opposite sides of a movable diaphragm. The control valve means includes an adjustable means for inversely varying the apertures or openings immediately adjacent the check valves and correspondingly varying the pressure in the flow passageways to the discharge sides of the throttling valve means. The passageways between the respective throttling valve means and control valve means defines a pair of pressure chambers or cavities. Conduit means interconnect each of such pressure cavities with a corresponding pressure chamber of the hydraulic actuator to establish balancing pressures on the opposite sides of the diaphragm.

If the apertures are set for essentially equal flow rates, corresponding pressures will be established in the pressure cavities and transmitted through the passageways to the corresponding chambers of the hydraulic actuator. The movement of the hydraulic actuator will then position the throttle valve to an established equal flow. If the apertures are adjusted to increase the flow through the one passageway and correspondingly decrease the flow through the opposite passageway, corresponding pressure signals will be transmitted to the hydraulic actuator to move the throttle valve means and adjust the flow through the two inlets until equal pressures are established in the pressure cavities and in the chambers of the hydraulic actuator.

Applicant has found that accurately proportioned flow rates can readily be maintained through the respective flow passages by controlling the restriction ratio of the apertures.

In a particularly novel and satisfactory system, the check valves and apertures are mounted in laterally spaced coplanar relationship to define a pair of parallel paths within the valve to a common outlet. Each of the check valves is preferably provided with a thermal release control to prevent excessive pressure buildup downstream of the blender assembly. A valve rod is slidably mounted in the body portion between the two apertures. An adjustment shaft is threaded into the one end of the aperture adjusting valve rod and rotatably fixed within the housing. Rotation of the shaft results in longitudinal movement of the valve rod and the relative ratio of the opening of the apertures. Suitable lock means may be provided to lock the valve rod in place.

A throttle valve includes a valve member slidably mounted within the wall between the parallel paths. The opposite ends of the valve member cooperates with valve orifices in the respective parallel paths to throttle the flow therethrough. Further, the ends of throttle valve member are specially shaped to provide direct proportional changes in the orifice area with linear movement of the valve member and the diaphragm of the hydraulic actuator to prevent abrupt changes in flow with a resulting hunting or pressure oscillating condition.

It has been found that the present invention provides a simple and inexpensive system for the dispensing of gasoline products or the like.

The drawings furnished herewith illustrate the best mode presently contemplated by the inventor for carrying out the subject matter of this invention and clearly discloses the above advantages and features as well as others which will be readily understood from the following description.

In the drawings:

FIG. 1 is a diagrammatic illustration of a gasoline dispensing system constructed in accordance with the present invention;

FIG. 2 is an enlarged vertical section through a blending valve assembly constructed in accordance with the present invention;

FIG. 3 is a top elevational view of the valve assembly shown in FIG. 2.

Referring to the drawing and particularly to FIG. 1, a gasoline dispensing system is shown employing three separate dispensing pumps 1, 2 and 3 for respectively dispensing a premium grade gasoline, a regular grade gasoline and an intermediateor blend" grade gasoline respectively. The premium" grade pump 1 is connected directly by a conduit or line 4 to a premium grade storage tank 5. The regular grade dispensing pump 2 is similarly connected by a conduit 6 directly to a regular" grade storage tank 7. The blend" grade dispensing pump 3 is interconnected through a blending valve 8, constructed in accordance with the teaching of the present invention, to both the premium grade line 4 and the regular grade line 6. The blending valve assembly 8, which is more clearly shown in a particularly novel construction in FIGS. 2 and 3, is adapted to blend any predetermined ratio of the premium grade and the regular grade gasolines to produce an intermediate octane rated gasoline which can be sold for an intermediate price. Each of the three pumps 1, 2 and 3 is constructed and interconnected to discharge a single product in contrast to the approach which has heretofore been suggested wherein each of the pumps is individually interconstructed with an adjustable means to selectively discharge any one of a plurality of different octane ratings. The dispensing pumps 1, 2 and 3 therefore may be of any well-known or any other construction such as presently widely employed in the dispensing of gasoline. Generally, each pump 1, 2 and 3 includes a register 9 having gallonage display portion 10 and a total cost display portion 11 driven from a single meter 12. A per gallon display portion 13 is also provided. An internal adjustment of any well-known construction permits varying of the setting of the display portion 13 with an automatic adjustment of the total cost display portion meter coupling ratio. As the structure and operation of the pumps 1, 2 and 3 are well-known, no further description thereof is given.

Referring particularly to FIGS. 2 and 3, the illustrated blending valve assembly 8 includes a valve body 14 having a first inlet 15 interconnected to the premium line 4 and a second adjacent valve inlet 16 interconnected to the regular grade line 6. A head 17 is bolted or otherwise suitable interconnected to the opposite end of the valve body 14 with a sealing gasket 18 disposed therebetween to maintain a fluidtight connection. The head 17 is generally cup-shaped and when assembled with the valve body 14, defines an output chamber 19 with an outlet 20 centrally formed therein. The output is similarly connected by corresponding check valves 21 and 22 to a pair of similar fiow passageways for the two basic grades of gasoline.

The pair of parallel flow passageways leading from the respective inlets 15 and 16 to the common outlet 20 are essentially identical. Consequently, the passageway for the valve inlet 15 interconnected to the premium grade line 4 is described in detail with the corresponding elements of the opposite passageway identified by similar primed numbers for purposes of simplicity and clarity of explanation.

The valve inlet 15 extends inwardly to a throttling valve unit 23 including an orifice 24 having an axis normal to the axis of the valve inlet 15. A pressure cavity or chamber 25 is provided to the discharge side of the throttling orifice 24. The cavity 25 is interconnected to the common output chamber 19 in the head 17 of the valve by a control opening or aperture 26 forming a part of a control valve unit 27.

An aperture control member 28 is slidably mounted within the valve body 14 between the two valve pressure cavities 25 and 25 and immediately adjacent the apertures 26 and 26'. The lateral displacement of the member 28 from the centered position shown varies the flow aperture cross-sectional area of the apertures 26 and 26' in an inverse manner. This in turn is reflected in a variation in the pressure in the pressure cavities 25 and 25'. The two pressures of the two parallel flow passageways are transmitted to a hydraulic diaphragm actuator 29 interconnected to position the throttling valve unit 23 in such a manner as to produce a predetermined flow ratio of the premium grade gasoline and the regular grade gasoline to outlet 20.

More particularly, in the illustrated embodiment of the invention, the main throttle valve unit 23 is provided with the circular orifices or openings 24 in a lateral wall 30 between cavity 25 and inlet 15. A valve member 31 is slidably disposed within an opening in the center of the valve body 14 with the end aligned with orifice 24 and constructed as a frustoconical element 32. A pair of annular seals 33 are disposed within a central recess in the valve member 31 and slidably engage the adjacent wall of the valve body to provide a liquidtight seal preventing interchange of liquid between the two inlets. A positioning rod or shaft 34 extends through the valve member 31 and is pinned or otherwise secured thereto as at 35. The one end of shaft 34 projects laterally through the throttle orifice 24 and the pressure cavity 25 into the hydraulic actuator 29. The opposite end of the shaft 34 projects from the valve member 31 in the opposite direction through the throttle orifice 24 and the pressure cavity 25'. Consequently, with the valve member 31 centrally located within the body, the throttling valve ends 32 and the projection of the shafts 34 through the orifices 24 and 24' provide a corresponding flow opening into the two pressure cavities 25 and 25.

The opposite ends of the valve member 31 terminate in the frustoconical valve ends 32 and 32' aligned with the valve orifices 24 and 24 respectively. Movement of the valve member 31 toward and away from the corresponding orifices directly varies the orifice area and thereby the flow path. The tapered construction results in proportional linear variation in the orifice area in accordance with the linear movement of the shaft 34 and attached member 31. a

The hydraulic actuator 29 for shaft 34 is a known diaphragm-type unit having a cup-shaped base 36 bolted or otherwise interconnected to the side of the valve body 14 immediately adjacent the pressure chamber 25. The base 36 includes a hub 37 extending into an opening to the premium grade passageway 25 and defining a supporting bearing for the valve shaft 34. The hydraulic actuator 29 includes an outer cup-shaped cover 38 secured to the base with a diaphragm 39 spanning the chamber and clamped completely about the peripheral edge thereof between the mating portions of the base 36 and cover 38.

The shaft 34 extends through hub 37 and is clamped to the diaphragm 39 by a pair of opposed discs 40 and 41 on the opposite sides of the diaphragm. The position of the diaphragm 39 directly controls the position of the valve shaft 34 and the valve member 31. The diaphragm 39 defines a first pressure chamber 42 to one side of the diaphragm and a second pressure chamber 43 to the opposite side of the diaphragm.

The first pressure chamber 42 is interconnected to the immediately adjacent flow passageway or cavity 25 by a small opening 44 provided in the hub or bearing portion 37 of the base 36. The corresponding side of the diaphragm 39 is therefore subjected to the pressure established in the pressure cavity 25 by the flow of fluid through the throttle valve orifice 24 and the aperture 26.

The opposite pressure cavity 25' of the blending valve assembly is interconnected by a pressure conduit 45 to the opposite chamber 43 of the hydraulic actuator 29 to apply the corresponding pressure to the other side of diaphragm 39. The hydraulic actuator diaphragm 39 is therefore positioned in accordance with the relative pressures in the cavities 25 and 25' which in turn are controlled by the setting of the hydraulic valve member 31 and the control valve member 28.

ln the illustrated embodiment of the invention, the aperture control member 28 is a cylinder slidably disposed within the valve body 14 immediately outwardly of the throttle valve member 31 and projecting laterally into both of the pressure cavities 25 and 25' with the member 28 centrally located as shown in HQ 2. An annular seal 46 is disposed within an encircling recess in one end of the cylinder to seal the slide opening and prevent interchange of fluid between the two cavities. A tapped opening 47 is provided in the right end of the member 28 coaxially of the member. An adjustment shaft 48 threads into the tapped opening and extends outwardly through an opening in the valve body 14. A threaded plug 49 is secured within the opening and compresses a sealing gasket 50 to seal the opening. The shaft 48 extends through the plug 49 which is sealed by suitable O-ring seal 51. Snap rings 52 are similarly attached in corresponding recesses in the shaft 48 to the immediate end faces of the plug 49. This permits rotatable motion of the shaft 48 but prevents axial movement thereof.

The periphery of the cylinder 28 is provided with a longitudinal guide groove 53 in the surface immediately adjacent the exterior wall of the valve body 14. A small guide pin 54 is threaded through an appropriate opening in the valve body and projects into the groove 53 to prevent rotation of the cylinder while permitting axial or longitudinal movement within the valve body.

A small bleed passageway 55 interconnects the inner end of the tapped opening to the groove to bleed any fluid trapped under the adjusting screw back to the corresponding righthand passageway or cavity 25 in the valve body 14.

Rotation of the shaft 48 therefore results in the longitudinal movement of the cylinder 28 to thereby vary the positioning of the opposite ends of the member 28 with respect to the pres sure cavities. This in turn establishes a variable aperture 26 and 26 at the discharge ends of the pressure cavities and 25'. if the apertures 26 and 26' are set for equal flow rates and the throttle valve member 31 is centrally located, equal pressures will be established in the two pressure cavities 25 and 25' and apply corresponding equalized pressures to the actuator chambers 42 and 43 on the opposite side of the diaphragm 39. This will hold the throttle valve in the central location to maintain the equal flow rate.

If the adjusting or control shaft 48 is rotated to move the cylinder 28 to the right, as viewed in the drawing, it will provide for an increased flow of the premium grade product through the left passageway and cavity 25 in FIG. 2 of the drawing and a corresponding reduced flow through the opposite passageway and cavity 25. The increased flow results from a decreased pressure in the premium pressure cavity which is transmitted through the small passageway to the diaphragm. Simultaneously the opposite pressure cavity establishes an increased pressure which is applied to the opposite side of the diaphragm via the pressure conduit. This will tend to shift the diaphragm, the attached shaft and the valve body to the right thereby increasing the opening of the premium grade orifice and closing the regular grade orifice flow in a corresponding linear manner. This tends to reverse the pressure conditions in the two passageways. The differential pressure thus is applied to the actuator until the valve body of the throttling valve is set to establish a predetermined flow ratio, at which flow equal pressures are established in the two pressure cavities 25 and 25' and applied to the diaphragm 39. At this point, the diaphragm 39 and the attached valve member 31 are held in a corresponding position to maintain the desired flow ratio. The position of control shaft 48 and member 28 therefore determine the proportion of the flow through the valve body and thereby the final blend.

In the illustrated embodiment of the invention, a worm 56 is secured to the outer end of the control shaft 48. A pinion 57 is rotatably mounted within a suitable bracket 58 projecting outwardly of the valve body 14 and located to mesh with the worm 56. An adjusting dial 59 is provided to permit manual adjustment of the position of the cylinder 28. Suitable indicia may be provided on the adjusting dial to allow convenient positioning for a desired flow ratio.

The pressure cavities 25 and 25 are connected to the common outlet chamber 19 by the similar check valves 21 and 22. In the illustrated embodiment of the invention, each check valve includes a resilient faced valve member 60 secured to a hollow stem 61 which is journaled in a hub 62 in the head 17. A coil spring 63 encircles the hub 62 and resiliently holds the valve member 60 in engagement with a suitable valve seat 64 encircling the aperture 26. A small thermal relief valve 65 is supported within the hollow stem 61 of the check valve 21. The relief valve 65 prevents excessive pressure buildup downstream of the blending valve assembly 8.

The operation of the blending valve assembly 8 is controlled by the relative pressure drops created by the adjustable apertures 26 and 26 and the adjustable throttle valve orifices 24 and 24'. The adjustable apertures 26 and 26' are inversely varied by the manual positioning of the cylindrical member 28. The dispensing pump 3 is turned on to establish pressurized flow through the valve assembly 8, causing the check valves 21! and 22 to open and discharge a blended liquid from the pump. The flow passing through the throttle valve orifices 24 and 24' and the apertures 26 and 26' creates pressure conditions within the cavities 25 and 25' related to the flow. The amount of pressure available to each cavity is directly related to the amount of flow through the adjacent aperture. With the manually set control cylinder 28 and the throttle valve member 31 centrally located, identical flow passageways are created and consequently corresponding pressure conditions exist in cavities 25 and 25 which pressures are applied to the opposite sides of the diaphragm 39 of the hydraulic actuator 29. The equal flow is established and maintained. If the ratio is to be varied, the adjusting dial 59 and attached shaft 48 are rotated to move the cylindrical member 28 in a corresponding direction. For example, movement of the cylindrical member to the left, closes the aperture 26 for the premium grade gasoline and correspondingly increases the aperture 26' for the regular graizle gasoline. This will permit greater flow of regular gasoline and reduce flow of premium gasoline. The reducing or closure of the premium grade gasoline aperture or opening will increase the pressure in the cavity 25 and apply a corresponding signal to the one chamber 42 of the hydraulic actuator 29. Simultaneously the opening of the aperture 26 for the regular grade gasoline reduces the pressure in the cavity 25 and transmits the reduced pressure via the pressure conduit 45 to the opposite pressure chamber 43 of the hydraulic actuator 29. As a result, the throttle valve member 31 moves to the left in the illustrated embodiment of the invention to throttle the premium grade gasoline flow and increase the regular gasoline flow. The closing of the premium grade gasoline throttle valve orifice 24 decreases the pressure in the cavity 25 as a result of the greater drop across the throttling valve orifice 24. Simultaneously,'the opening of the throttle valve orifice 24' for the regular gradegasoline increases the pressure of cavity 25'. The throttle valve member 31 is moved until a new pressure balance is obtained in the hydraulic actuator 29 at which time the valve member 31 is held stationary to provide the desired proportional flow.

The flow from the valve assembly 8 is discharged through the pump 3 and particularly meter 12 which drives the pump 3 to record the gallonage and total cost in accordance with the usual system of gasoline dispensing.

The present invention thus provides a simplified means for providing a multiple or dispensing of a blended products as well as the basic liquid products and the like.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

Iclaim:

1. In a gasoline dispensing system having three dispensers for dispensing three grades of gasoline from a first storage tank connected to one dispenser and a second tank connected to a second dispenser, the third dispenser being connected to both tanks, a fluid mixer comprising:

a mixer body having a pair of inlets;

a common outlet connecting to the third dispenser and defining a passageway from each said inlet to the common outlet; throttling valve means including a valve body slidably disposed laterally in said mixer body and including a valve seat in each said passagewayin axial alignment with said valve body, for inversely varying the opening through said passageways; control valve assembly having a control valve body slidably disposed laterally in said mixer body intermediate said throttling valve means and said outlet, and a control valve orifice disposed in each said passageway with the ends of said control valve body terminating at said control orifices;

selector means for sliding said control valve body across said control valve orifices; and

actuator means being responsive to flow through said control valve orifices for operating said throttle valve means to equalize pressure insaid passageways.

2. The gasoline dispensing system of claim 1 wherein said selector means has a manually adjustable means connected to said control valve body for determining the mixture of said third grade, and said actuator means is a pressure actuator having a movable member and a pair of pressure input chambers to the opposite sides of said movable member, each chamber communicating with one said passageway, said actuator means having a connector from said movable member to said throttle means to position said valve member in accordance with the relative pressure levels in said passageways.

3. The fluid mixer of claim 1 and including check valve means for opening and closing said passageways in response to pressure in said passageways.

4. A fluid dispensing apparatus for mixing a first and second liquid in varied proportions, comprising;

a body having a central portion and defining a pair of flow passageways to either side of said central portion, said passageways having orifices at said central portion, the orifices being aligned on a first lateral axis of said body;

a throttle valve having a valve body slidably disposed in said central portion along said lateral axis, the valve body extending outward into said passageways to said orifices;

a control means for inversely varying the flow through said passageways, said control means having a control member body slidably disposed through said central portion on a second lateral axis upstream of said throttle valve, said control member being slidable into said passageways to inversely restrict the flow area of said passageways; and

pressure actuator means connected to said throttle valve and communicating with the passageways intermediate said first and second axes, for operating said throttle valve to equalize pressures in said passageways.

5. The fluid dispensing apparatus of claim 4 wherein said throttle valve includes a positioning shaft extending outwardly from one end through one of said orifices and a balancing shaft stub extending from the opposite end through the second of said orifices.

6. The fluid dispensing apparatus of claim 4 wherein the ends of said throttle valve are frustoconically shaped to produce a smooth proportional change in the orifice opening with movement of the valve member.

7. A fluid dispensing apparatus for delivery of different ratios of a first and second liquid through a pair of flow passageways, comprising:

a body portion defining said passageways;

valve means in said flow passageways for inversely opening and closing said passageways;

control means disposed in spaced relation from said valve means for varying the flow resistance of said passageways, said control means including a control shaft disposed for movement laterally of said passageways with the ends of said control shaft terminating in said passageways and inversely varying the cross-sectional flow areas thereof;

an actuator having a diaphragm and a pair of opposed pressure input means disposed to the opposite sides of said diaphragm, said input means connecting respectively to the passageways between said control shaft and said valve means;

means connecting said diaphragm to said valve means;

said control shaft having an axial end opening; and

adjusting means including a positioning rod threaded into said axial opening and rotatably mounted in said body portion for axially moving said control shaft relative to said passageways; the inner end of said axial opening having a vent to prevent trapping of fluid within said opening. 

1. In a gasoline dispensing system having three dispensers for dispensing three grades of gasoline from a first storage tank connected to one dispenser and a second tank connected to a second dispenser, the third dispenser being connected to both tanks, a fluid mixer comprising: a mixer body having a pair of inlets; a common outlet connecting to the third dispenser and defining a passageway from each said inlet to the common outlet; a throttling valve means including a valve body slidably disposed laterally in said mixer body and including a valve seat in each said passageway in axial alignment with said valve body, for inversely varying the opening through said passageways; a control valve assembly having a control valve body slidably disposed laterally in said mixer body intermediate said throttling valve means and said outlet, and a control valve orifice disposed in each said passageway with the ends of said control valve body terminating at said control orifices; selector means for sliding said control valve body across said control valve orifices; and actuator means being responsive to flow through said control valve orifices for operating said throttle valve means to equalize pressure in said passageways.
 2. The gasoline dispensing system of claim 1 wherein said selector means has a manually adjustable means connected to said control valve body for determining the mixture of said third grade, and said actuator means is a pressure actuator having a movable member and a pair of pressure input chambers to the opposite sides of said movable member, each chamber communicating with one said passageway, said actuator means having a connector from said movable member to said throttle means to position said valve member in accordance with the relative pressure levels in said passageways.
 3. The fluid mixer of claim 1 and including check valve means for opening and closing said passageways in response to pressure in said passageways.
 4. A fluid dispensing apparatus for mixing a first and second liquid in varied proportions, comprising; a body having a central portion and defining a pair of flow passageways to either side of said central portion, said passageways having orifices at said central portion, the orifices being aligned on a first lateral axis of said body; a throttle valve having a valve body slidably disposed in said central portion along said lateral axis, the valve body extending outward into said passageways to said orifices; a control means for inversely varying the flow through said passageways, said control means having a control member body slidably disposed through said central portion on a second lateral axis upstream of said throttle valve, said control member being slidable into said passageways to inversely restrict the flow area of said passageways; and pressure actuator means connected to said throttle valve and communicating with the passageways interMediate said first and second axes, for operating said throttle valve to equalize pressures in said passageways.
 5. The fluid dispensing apparatus of claim 4 wherein said throttle valve includes a positioning shaft extending outwardly from one end through one of said orifices and a balancing shaft stub extending from the opposite end through the second of said orifices.
 6. The fluid dispensing apparatus of claim 4 wherein the ends of said throttle valve are frustoconically shaped to produce a smooth proportional change in the orifice opening with movement of the valve member.
 7. A fluid dispensing apparatus for delivery of different ratios of a first and second liquid through a pair of flow passageways, comprising: a body portion defining said passageways; valve means in said flow passageways for inversely opening and closing said passageways; control means disposed in spaced relation from said valve means for varying the flow resistance of said passageways, said control means including a control shaft disposed for movement laterally of said passageways with the ends of said control shaft terminating in said passageways and inversely varying the cross-sectional flow areas thereof; an actuator having a diaphragm and a pair of opposed pressure input means disposed to the opposite sides of said diaphragm, said input means connecting respectively to the passageways between said control shaft and said valve means; means connecting said diaphragm to said valve means; said control shaft having an axial end opening; and adjusting means including a positioning rod threaded into said axial opening and rotatably mounted in said body portion for axially moving said control shaft relative to said passageways; the inner end of said axial opening having a vent to prevent trapping of fluid within said opening. 